**Abstract**

Cotton (*Gossypium hirsutum* L.) is the most produced natural fibre worldwide, and it contributes significantly to the economy of almost 80 cotton-producing countries. Given the high pest infestation, huge amounts of insecticides have been used in cotton production. However, this has resulted in the development of resistance from primary cotton pests and contamination of the environment. Furthermore, the reduction of beneficial insects and outbreaks of secondary pests have been observed. Many arthropod pests are associated with cotton, most of which belong to the orders Lepidoptera, Thysanoptera, and Hemiptera. Biocontrol agents play a critical role in preventing pests in most cotton-growing areas globally. Biological control of cotton pests forms part of integrated pest management as most of these pests have developed resistance against synthetic pesticides. This chapter focuses on the effects of some of the biopesticides, on cotton insect pests. It examines the control of cotton pests using microbial-based products *Bacillus thuringiensis*, *Beauveria bassiana*, *Helicoverpa armigera* nucleopolyhedrovirus and *Metarhizium rileyi*. Furthermore, the chapter summarizes the application of microbial biopesticides as well as the advantages and disadvantages of using these biocontrol agents in agriculture.

**Keywords:** Cotton, Insecticides, Microbial biopesticides, *Bacillus thuringiensis*, *Beauveria bassiana*, *Metarhizium rileyi*, Nucleopolyhedrovirus
